Vauxhall Insignia cold start

Since having the car, 2 years, the choke has never worked properly. As the choke shut off the car stalled.It always started again and was fine once warmed up. Recently i've had the head gasket replaced along with the cam belt. After this the car would not idle. The throttle body was changed and the coil pack was changed twice. Now the car runs once warmed up but the cold start problem is worse than ever. I have to rev the engine until it's up to temperature as it won't idle at all now. Once it's warmed up, after a good 5 minutes of revving, it runs ok.